na-adjective, noun
Used both as a mathematical term for an unbounded quantity and figuratively for something limitless or immense.
宇宙は無限大に広がっていると考えられている。
The universe is thought to extend infinitely.
彼の可能性は無限大だ。
His potential is infinite.
Compound of 無限 (mugen, 'limitless') and 大 (dai, 'large, great'), literally 'limitlessly large'. The exact historical derivation is uncertain, but the term is used in modern Japanese to express the concept of infinity.